Reaction of alpha-substituted acroleins with alcohols to form alkoxy-sigma-lactones



United States Patent Q REACTION OF tX-SIJBSTITUTED ACROLEINS WITHALCOHOLS TO FORM ALKOXY-fi-LACTONES Benjamin Thompson, Kingsport, Tenn.,assignor to Eastman Kodak Company, Rochester, N. Y., a corporation ofNew Jersey N Drawing. Application September 22, 1949, Serial No. 117,274

4 Claims. (Cl. 260- 3435) .This invention relates to the reaction ofa-substituted acroleins with alcohols in the presence of stronglyalkaline catalysts, to form alkoxy-e-lactones.

' It is known that unsaturated aldehydes react with alcohols in thepresence of a mineral acid catalyst to form acetals offl-alkoxyaldehydes (see United States Patent 2,288,211, dated June 30,1942). A related process comprising reacting a-substituted acroleinswith polyhydric alcohols in the presence of a small amount of acidcatalyst to form resinous products, is also known (see United StatesPatent 2,401,776, dated June 11, 1946). Acrolein is known to undergo thealdol condensation in the presence-v of an alkaline catalyst. It is alsoknown that acrylonitrile reacts with alcohols, in the presence of astrongly alkaline catalyst, with addition of the alcohol to the doublebond to form ,3-alkoxypropiononitriles.

Ihave now found that an a-substituted acrolein and an alcohol react, inthe presence of a strongly alkaline catalyst, in a novel and unexpectedmanner with the formation of new a-lactones, instead offi-alkoxyaldehydes which would have been expected to form by means ofthealcohol splitting into its alkoxy'and hydrogen components and addingat either side of the double bond of the a.- substituted acrolein, e. g.methanol would be expected to react with a-methacrolein to produceB-methoxyisobutyraldehyde as follows:

After my surprising discovery, I found that such p-alkoxy aldehydes canbe obtained at temperatures below 0 0.,

thus the reaction of wmethacrolein with excess methanol in the presenceof sodium methylate at -20 C. results in the production ofB-methoxyisobutyraldehyde, .To

isolate this product at ambient temperatures, the catalyst should bedestroyed before the mixture is warmed up.

My invention, however, is not concerned with such prod ucts but onlywith my newly-discovered a-lactones and the process for their productionat temperatures in excess of 0 C.

The mechanism of the reaction can be illustrated using a-methacrolein,ethyl alcohol, and sodium ethoxide as the catalyst. Although the exactmechanism of thereac tion in the catalytic presence of sodium ethoxide,as follows;

The dimer then adds ethyl alcohol and the two aldehyde 2,725,387Patented Nov 29, 1 955 ice 2 groups react with each. other, one beingoxidized and the other reduced, to form an ethoxy-6-lactone:

This a-lactone is that of 'p-ethoxy-a-hydroxyan-trimethylvaleric acid.

2. The ok-methacrolein dimerizes in the catalytic presence of sodiumethioxide according to the vinyl head-tota'ilmechanism:

Then the dimer is deactivated, by the addition of ethyl Whereupon, thetwo aldehyde groups react with each other, one being oxidized-and theother reduced, to form an ethoxy-6-lactone:

CH2-OC2H5 GHQ-(5 02H, crn-o-ono f card-43:0

H2 Hz 0 CH -l-CHO' Carri- 45111 H v v H s This fi-lactone is that of aa-ethoxymethyl fi-hydroxyayy-dirnethylvaleric acid.

3. The a-methacrolein in the catalytic presence of so- 'dium ethoxideundergoes a reaction involving a hydrogen Then, the unsaturateddialdehyde atom on the tat-methyl group, which is'activated by thedouble-bond, forming an unsaturated dialdheyde:

CHi CH3 270E3 -CHO OHa- CHO IHz cage-0H0 adds ethyl alcohol:

OH: CHa(J-CHO 011150151 OH: I g H2 -O,Hz*=(., CHO CZH OCH-zH-CHOWhereup'on', the two aldehyde groups react with each other, one'bein'goxidized and the other reduced, to form an eth'oxy-E-lactone:

eatcrro 012350 om -hnono cgmoom-orr-dm This a-lactone is that of,6-ethoxy-6-hydroxy-e,' ,y-trimethylvaleric acid.

5. In 2 above, the two aldehyde groups may undergo oxidation-reductionto form:

This 6-lactone is that of 'y-ethoxymethyl -6-hydroXy-a,- dimethylvalericacid.

6. In 3 above, the two aldehyde groups may undergo oxidation-reductionto form:

This B-lactone is that of ut-ethoxymethyl-ii-hydroxy-w,q -vdimethylvaleric acid.

These illustrative possibilities are based on a reaction wherein 2 molesof a-methacrolein are reacted with 1 mole of ethyl alcohol resulting in6 possible isomers of trimethylethoxy--valerolactone. However, it isalso possible to react these components in the molar ratios of 3 :l(oi-substituted acrolein to alcohol), 4: 1, 5:1, 6:1, etc., resulting inthe formation of higher molecular weight alkoxy-fi-lactones consistingmainly of a combination of three or more molecules of a-substitutedacrolein with one molecule of alcohol. Such products appear to con! sistof alkoxy-a-valerolactones with additional molecules of thea-substituted acrolein intramolecularly bonded in chain-like sequencethereto; e. g., the dimer may have the formula C1oH1sO3, the trimer mayhave the formula C14H24O4, the quadrimer the formula CmHsuOs, etc., eachdiffering by C4HsO which is the molecular formula for the a-substitutedacrolein, CH2=C(CH3)CHO, utilized in this exemplary series.

Another variation is to employ two or more. different a-substitutedacroleins and an alchol, thus forming an. alkoxy-a-lactone having thesubstituted groups of both acroleins. Thus, while a-methacrolein reactswith ethyl alcohol to give an alkoxy-B-lactone of the formula CIOHIBOB(e. g., ethoxymethyl-dimethyl-6-valerolactone), and a-ethacrolein reactswith ethyl alcohol to give an alkoxy-a-lactone of the formula C12H22O3(e. g. an ethoxymethyl-diethyl-fi-valerolactone), a reaction comprisingboth of these lZ-SllbStltuted acroleins with ethyl alcohol would giveboth of the above alkoxy-B-lactones and, in addition, anotheralkoxy-6-lactone of the formula CuHzoOa (e. g. anethoxymethyl-methyl:ethyl-E-valerolactone). Also, two or more alcoholsmay be employed with correspondingly self-evident results.

The E-lactones produced according to my invention havea wide range ofproperties which make them valuable.

cellulose esters. When employing polyhydric alcoholsin the-processofmy-inventiome. g. glycerol, pentaerythritol, etc., the high boilingproducts obtained have application 4.- in the synthetic coatingsindustry as modifiers for alkyd resins, etc.

It is, therefore, an object of my invention to provide new 6-lactones. Afurther object is to provide a process for preparing such fi-lactones.Other objectives will become apparent hereinafter.

In accordance with my invention, 6-lactones are pree pared by reactingan tat-substituted acrolein with an alcohol, in the presence of astrongly alkaline catalyst a temperatures in excess of 0 C.

My invention embraces the use of tit-substituted acroleins having theformula:

wherein R and R each represents a hydrogen atom or an alkyl radical.Advantageously the sum of the carbon atoms in R and R taken'togetherdoes not exceed 3, thus R and R each represents a hydrogen atom or amethyl, ethyl, propyl or isopropyl radical. Most advantageously, Rrepresents a hydrogen atom, and R represents either a hydrogen atom or amethyl radical.

Such tat-substituted acroleins include a-methacrolein, a-ethacrolein,a-n-propylacrolein, u-n-butylacrolein, a-isopropylacrolein, a-sec.butylacrolein, and a-isobutylacrm lein.

The reacting alcohols employed in the process of my invention can beselected from among any of the aliphatic and aromatic mono andpolyhydric alcohols. Advanta geously, I employ at least one of thealcohols containing from 1 to 10 carbon atoms selected from among thealkanols, the alkoxyalkanols, the hydroxyalkoxyalkanols, thealkoxyalkoxyalkanols, the alkane diols, the alkane triols, the alkanetetrols, and the aralkanols containing from 7 to 8 carbon atoms.Especially useful ii-lactones are obtained by employing alcoholscontaining from 1 to 4 carbon atoms. Examplary alcohols which can beemployed include methyl alcohol, ethyl alcohol, isopropyl alcohol,propyl alcohol, butyl alcohol, tertiary butyl alcohol, isobutyl alcohol,Z-ethylhexanol, octyl alcohol, nonyl alcohol, glycols (e. g. ethyleneglycol), hexane diols, diethylene glycol, Cellosolve (viz.fi-ethoxyethyl alcohol), Carbitol (viz. diethylene glycol monoethylether), 13- hydroxyethyl alcohol, ,B-hydroxypropyl alcohol, glycerol,pentaerythritol, 2,2,,4,4-tetramethylol cyclohexanol, sorbitol, etc.

The reaction can be catalyzed by employing at least one of the stronglyalkaline compounds selected from the alkali metal and quaternaryammonium bases. Advantageously, I employ an amount of such catalystsfrom about 0.1 to about 5 molar per cent of the cit-substitutedacroleinbeing reacted, although larger or smaller amounts can beemployed. Such catalyst bases include the alkali metals, alkali metaloxides, hydroxides, nitrides, amides, alcoholates, etc., and thearalkyltrialkyl quaternary ammonium and the tetraalkylquaternaryammonium hydroxides and alcoholates where the alkyl groups contain fromcan beadvantageously prepared from any of the alcohols used in thereaction itself as defined above. Typical alcohols which can be employedare also listed above.

Typical examples of such catalysts which I can employ advantageouslyinclude sodium methylate, sodium ethylate, potassium n-propylate,tetramethylammonium isobutylate, benzyltrimethylammonium n-butylate,potassium fi-ethoxyethylate, potassium oxide, potassium hydroxide,sodium nitride and sodium amide.

Upon completion of the reaction being catalyzed, the

catalyst can be destroyed, if desired, by neutralization with anequivalent quantity of acid, e. g. H2804, or in the case of thequaternary ammonium catalysts, they can be destroyed by heating thereaction mitxure, e. g. to about 150 C. or higher.

The advantageous temperature range employed in carrying out my processis from 0-75 C. However, higher temperatures can be used depending onthe properties of the reactants employed. Thus the reaction can becarried out at its reflux temperature. The most advantageous temperaturerange is from to 50 C.

A nitrogen atmosphere is advantageously used in practicing my invention,but any inert atmosphere can be used, or the reaction can be carried outin a closed system so that there is little chance of contact oroxidation of the acrolein by oxygen which might cause undesirablepolymerization. An inert atmosphere is desirable but not critical.

A polymerization inhibitor such as 'hydroquinone, pphenylenediamine,etc., can be employed in practicing my invention, but such an inhibitoris not necessary. If an inhibitor such as hydroquinone is used, it canbe destroyed, prior to separation of the desired lactones from thereaction mixture, by air'oxidation or extraction.

The following examples will serve to illustrate further the practice ofmy invention. 7

Example 1 Three moles of anhydrous ethanol and 0.1 mole of metallicsodium were fed into a 3-neck flask containing a stirrer, feed burette,reflux condenser, thermometer, and nitrogen inlet tube. When the sodiumhad dissolved, the remaining oxygen was flushed out of the flask withnitrogen. The mixture was cooled to 20 C. in a 0 C. bath. Then 2.5 molesof a-methacrolein was fed into the stirred mixture at a rate such thatthe heat of reaction could be removed by cooling. The temperature wasmaintained in the 10-30 C. range. This required approximately l /zhours. The reaction mixture was then vacuum distilled without furthertreatment. Very little a-methacrolein remained unreacted. The unreactedethyl alcohol was distilled ofl and the pressure reduced to 1 mm. of Hgpressure. The main product, C10H1803 (e. g., anethoxy-trimethyl-fi-valerolactone) was recovered by distillation in a60-75% yield. The C10H1803 had a boiling point between 92-95 C. at 1 mm.of Hg pressure. The distillation was continued and a second fi-lactone,

C14H24O4, boiling at 135 C.140 C. at 1 mm. Hg of pressure, was obtainedin a yield of 10-20%. Theprodnot having the formula C10H1803 has thefollowing structural formula:

which is alpha, gamma-dimethyl-gamma-ethoxymethyldelta-valerolactone.

Example2 The procedure of Example 1 was repeated except that 2.5 molesof a-ethacrolein was used instead of a-methacrolein. The main productwas B-lactone, C12H22O3, boiling at ll0-115 C. at 1 mm. of Hg pressure.This product was an ethoxy-diethyl-methyl-6-valerolactone. Additionaldistillation resulted in the recovery of higher molecular weightproducts in small yields.

Example 3 The procedure of Example 1 was repeated except that 18 molesof n-butanol was used instead of ethyl alcohol, 0.3 mole sodium insteadof 0.1 mole, and 6 moles of a-methacrolein instead of 2.5 moles, andexcept that the reaction was run for 3 hours instead of 1 /2, afterwhich time the catalyst was neutralized with 0.15 mole of 50%'a'temperature of from 40 to 50 C. The reaction mix- The main productwas a 70-85% yield of a CizHzzOs, boiling at H2804.buto'xy-trirnethyl-a-valerolactone,

C. at 3mm. of Hg pressure.

Example 4 The procedure of Example 1 was repeated except that 1.7 molesof Cellosolve (ethylene glycolmonoethyl ether) Example 5 One mole ofethylene glycol and 0.1 mole of metallic sodium were fed into a 3-neckflask equipped as in Exam ple 1. When the sodium had dissolved, theremaining oxygen was flushed out of the flask with nitrogen. The

mixture was cooled to 20 C., and 2.5 moles of a-methacrolein was fedinto the glycol-catalyst mixture at 15 to 20 C. with constant stirring.The reacting mixture was then stirred for approximately 4 hours at 25 to30. C. The resulting product was a viscous syrup which was treated withacid as in Example 3 and washed with water in order to neutralize andremove the alkaline catalyst. The oil resulting was then distilled on amolecular still. mono and dilactone ethers of the glycol, viz. C1oH1aO4and C18H3006. The structural formulae might be any of six possibleisomers as indicated previously. Selecting the isomer numbered 1 above,the diether CmHauOs would have the following configuration:

CH3 om 'By varying the amount of sodium from 0.01 to 0.1 mole andvarying the quantity of a-methacrolein from 2.0 to 3.5 moles, similarresults were obtained. The proportion of the monoether to the dietherdepends upon the molar ratio of the a-methacrolein to the glycol.

Example 6 In a manner similar to that set forth in Example 1,

" 0.3 mole of sodium was dissolved in .15 moles of 2-ethyl-.

hexanol. The reaction vessel was then flushed'out with nitrogen. Then,over a period of from 3 to 4 hours, 6

moles of a-methacrolein was fed into the 2-ethylhexanolv solution whichwas constantly stirred and maintained at ture was allowed to stand for 2hours after all of the reaction heat had disappeared. Then the alkalinecatalyst was neutralized with dilute acid as in Example 3 and washedout. A 45% yield of a 2-ethylhexoxy-5-valerolactone of the formulaC16H3003 was obtained. This 6- lactone has a boiling point of 15J C. at1 mm. of Hg pressure. In addition to this principal product, a yield ofabout 50 to 55% of higher condensation products was obtained.

Example 7 Six moles of u-methacrolein and six moles of ethyl alcoholwere fed into a reaction vessel. The mixture was cooled to 20 C. and0.02 mole of catalyst comprising a 25% solution oftrimethylbenzylammonium butoxide dissolved in butanol was fed into thevessel gradually over a period of approximately one hour; the rate offeeding was such that the reaction temperature was maintained between 20and 35 C. The mixture was stirred for an additional hour and then thecatalyst was destroyed by heating the mixture above C. The alkoxy-6-lactone, C10H1s03, boiling at 92-95 C. at 1 mm. of Hg pressure, wasrecovered by distillation in a yield of less than 20%. Furtherdistillation was used to recover the main product, an alkoxy-fi-lactonewith the empirical The major product comprised a mixture of the' formulaCnHzrOa boiling at 135-140 Q, at 1 of Hg pressure, in a 45-60% yield.

Example 8 40 parts by weight of the alkoxy-B-lactone of the formulaC12H22O3 (prepared from u-ethacrolein and ethyl alcohol by the methodset forth in Example 2) were mixed with 100 parts by weight of celluloseacetate-propionate. The result was a homogeneous plastic of medium flowhaving a moisture absorption of 2.6%, 0.1% loss by leaching, and only0.7% loss in the standard heat test for permanence.

My process is advantageously carried out on an industrial scale in thefollowing continuous manner. A solution of the ran-substituted acrolein,the desired alcohol, the alkaline catalyst and the fi-lactone product ismaintained between approximately and 50 C. in a suitable vessel. Aportion of this main body of solution is substantially continuouslywithdrawn and divided into two parts. One part of this withdrawnsolution is subjected to cooling by means of a suitable heat exchanger(in order to maintain the reaction mixture within the temperature rangedesired for the particular reaction being conducted) and additionalOL-SllbSlllUtd acrolein, alcohol and catalyst are added, whereupon thispart of the withdrawn solution is returned to the main body of thesolution. A rapid, turbulent dispersal of the catalyst into the solutionis important. The other part of the solution, which was withdrawn fromthe main body of the solution, is allowed to react for an additionallength of time, and-then the catalyst is neutralized and the a-lactoneseparated therefrom. The neutralization of the catalyst can be carriedout by using a dilute mineral acid. The salt, thus formed, dissolveswhen water is added and can be separated from the crude alkoxy-e-lactoneproduct as a lower layer in the case of higher alcohols, or as a lowerphase after distilling oil the unreacted tat-substituted acrolein andalcohol.

In a manner similar to that illustrated in the foregoing examples,a-n-propylacrolein, ot-l'l-blltYlflCIOlill, a-isobutylacrolein, etc. canbe reacted separately or in various proportions with methyl, ethyl,n-propyl, isopropyl, nbutyl, isobutyl, benzyl alcohol, etc. separatelyor mixed together, thereby producing various alkoxyn-lactones andmixtures thereof. Thus ot-n-propylacrolein can be reacted with benzylalcohol in the presence of potassium n-propylate to produce abenzoxy-E-lactone, possiblya-benzoxymethyl-ow-di-n-propyl-e-valerolactone or an isomer thereof. Or,e-isopropylacrolein can be reacted with nbutyl alcohol in the presenceof sodium isobutylate to produce an n-butoxy-H-lactone, possiblyfJ-butoxy-otmethyl-a,'y-di-n-butyl-6-valerolactone or an isomer there.-of. Alternatively, Ot'lSOblllYlflCIOlCll'l can be reacted with isopropylalcohol in the presence of potassium [,R-ethoxy-v ethylate to produce anisopropoxy-B-lactone, Possibly cisopropoxy-ayrdiisobutyl-fi-valerolactone or an. isomer thereof.

What I claim as my invention and desire to secure by Letters Patent ofthe United States is:

1. A process for the production of a substituted deltavalerolactone,said process comprising condensing methacrolein and an alcohol undersubstantially anhydrous conditions in the presence of a basiccondensation catalyst and distilling the condensate in the presence of abasic condensation catalyst.

2. A process for preparing B-lactones comprising reacting undersubstantially anhydrous conditions u-methacrolein with an alkane diolcontaining from 2 to 10 carbon atoms at a temperature in excess of 0 C.and in the catalytic presence of from 0.1 to 5 molar percent based onthe weight of ot-methacrolein of a strongly alkaline compound selectedfrom the group consisting of the alkali metals, the alkali metal basesand the quaternary ammonium bases, the ratio of the u-methacrolein toalkane diol being from 3:1 to lzl'whereby a-lactone molecules formedcontain a ratio of a-methacrolein groups to alkane diol groups of from6:1 to 2:1.

3 A process for preparing fi-lactones comprising re acting undersubstantially anhydrous conditions a.- methacrolein with ethylene glycolat a temperature of from 0 C. to C. in the catalytic presence of from0.1 to 5 molar percent based on the weight of a-methacrolein' of astrongly alkaline compound selected from the group consisting of thealkali metals, the alkali metal bases and the quaternary ammonium bases,the ratio of the u-methacrolein to ethylene glycol being from 3:1 to 1:1whereby the fi lactone molecules formed contain a ratio of wmethacroleingroups to ethylene glycol groups of from 6:1 to 2:1.

4. A process for preparing 6-lactones comprising reacting undersubstantially anhydrous conditions a-meth acrolein with ethylene glycolat a temperature of from 10 C. to 50 C. in the catalytic presence offrom 0.1 to 5 molar percent based on the weight of u-methacrolein ofsodium, said reaction being conducted in an inert atmosphere, the ratioof the a-methacrolein to ethylene glycol being from 3:1 to 1:1 wherebythe o-lactone mole.- cules formed contain a ratio of a-methacroleingroups to ethylene glycol groups of from 6:1 to 2:1.

References Cited in the file of this patent UNITED STATES PATENTS1,962,157 Seymour June 12, 1934 2,122,719 Kreimeier July 5, 19382,212,894 Allen Aug. 27, 1940 2,356,459 Kung Aug. 22, 1944 2,368,366Kyrides Ian. 30, 1945 2,428,015 Daniels'et al Sept. 30, 1947 2,429,799Bremner Oct. 28, 1947 2,504,680 Gresham Apr. 18, 1950 2,526,702 SmithOct. 24, 1950 FOREIGN PATENTS 608,985 Great Britain 1946 OTHERREFERENCES Curtman: Qualitative Chemical Analysis, 1932,

MacMillan Co., N. Y., pp. 4124-13.

1. A PROCESS FOR THE PRODUCTION OF A SUBSTITUTED DELTAVALEROLACTONE,SAID PROCESS COMPRISING CONDENSING METHAROLEIN AND AN ALCOHOL UNDERSUBSTANTIALLY ANHYDROUS CONDITIONS IN THE PRESENCE OF A BASICCONDENSATION CATALYST AND DISTILLING THE CONDENSATE IN THE PRESENCE OF ABASIC CONDENSATION CATALYST.